Graft ligament anchor and method for attaching a graft ligament to a bone

ABSTRACT

A graft ligament anchor comprises a graft ligament engagement member disposed in an opening in a bone, the graft ligament engagement member being arranged to receive a graft ligament alongside the engagement member, and a locking member for disposition in the opening, and at least in part engageable with the graft ligament engagement member. Movement of the locking member in the opening causes the locking member to urge the engagement member, and the graft ligament therewith, toward a wall of the opening, to secure the graft ligament to the wall of the opening. A method for attaching a graft ligament to a bone comprises providing an opening in the bone, inserting the graft ligament and a graft ligament engagement member in the opening, with the graft ligament disposed alongside a first portion of the engagement member, and inserting a locking member in the bone alongside a second portion of the engagement member, the locking member being separated from the graft ligament by the graft ligament engagement member. The method further comprises moving the locking member to cause the locking member to engage the graft ligament engagement member to urge the graft ligament engagement member, and the graft ligament therewith, toward a wall of the opening to secure the graft ligament to the wall of the opening.

FIELD OF THE INVENTION

[0001] This invention relates to medical apparatus and methods ingeneral, and more particularly to apparatus and methods forreconstructing ligaments.

BACKGROUND OF THE INVENTION

[0002] Ligaments are tough bands of tissue which serve to connect thearticular extremities of bones, or to support or retain organs in placewithin the body. Ligaments are typically composed of coarse bundles ofdense white fibrous tissue which are disposed in a parallel or closelyinterlaced manner, with the fibrous tissue being pliant and flexible,but not significantly extensible.

[0003] In many cases, ligaments are torn or ruptured as a result ofaccidents. As a result, various procedures have been developed to repairor replace such damaged ligaments.

[0004] For example, in the human knee, the anterior and posteriorcruciate ligaments (i.e., the ACL and PCL) extend between the top end ofthe tibia and the bottom end of the femur. The ACL and PCL cooperate,together with other ligaments and soft tissue, to provide both staticand dynamic stability to the knee. Often, the anterior cruciate ligament(i.e., the ACL) is ruptured or torn as a result of, for example, asports-related injury. Consequently, various surgical procedures havebeen developed for reconstructing the ACL so as to restore normalfunction to the knee.

[0005] In many instances, the ACL may be reconstructed by replacing theruptured ACL with a graft ligament. More particularly, with suchprocedures, bone tunnels are typically formed in the top end of thetibia and the bottom end of the femur, with one end of the graftligament being positioned in the femoral tunnel and the other end of thegraft ligament being positioned in the tibial tunnel. The two ends ofthe graft ligament are anchored in place in various ways known in theart so that the graft ligament extends between the femur and the tibiain substantially the same way, and with substantially the same function,as the original ACL. This graft ligament then cooperates with thesurrounding anatomical structures so as to restore normal function tothe knee.

[0006] In some circumstances the graft ligament may be a ligament ortendon which is harvested from elsewhere in the patient; in othercircumstances the graft ligament may be a synthetic device. For thepurposes of the present invention, all of the foregoing can becollectively referred to as a “graft ligament”, “graft material” or“graft member.”

[0007] As noted above, the graft ligament may be anchored in place invarious ways. See, for example, U.S. Pat. No. 4,828,562, issued May 9,1989 to Robert V. Kenna; U.S. Pat. No. 4,744,793, issued May 17, 1988 toJack E. Parr et al.; U.S. Pat. No. 4,755,183, issued Jul. 5, 1988 toRobert V. Kenna; U.S. Pat. No. 4,927,421, issued May 22, 1990 to E.Marlowe Goble et al.; U.S. Pat. No. 4,950,270, issued Aug. 21, 1990 toJerald A. Bowman et al.; U.S. Pat. No. 5,062,843, issued Nov. 5, 1991 toThomas H. Mahony, III; U.S. Pat. No. 5,147,362, issued Sep. 15, 1992 toE. Marlowe Goble; U.S. Pat. No. 5,211,647, issued May 18, 1993 toReinhold Schmieding; U.S. Pat. No. 5,151,104, issued Sep. 29, 1992 toRobert V. Kenna; U.S. Pat. No. 4,784,126, issued Nov. 15, 1988 to DonaldH. Hourahane; U.S. Pat. No. 4,590,928, issued May 27, 1986 to Michael S.Hunt et al.; and French Patent Publication No. 2,590,792, filed Dec. 4,1985 by Francis Henri Breard.

[0008] Despite the above-identified advances in the art, there remains aneed for a graft ligament anchor which is simple, easy to install, andinexpensive to manufacture, while providing secure, trouble-freeanchoring of the graft ligament, typically in the knee joint of amammal.

OBJECTS OF THE INVENTION

[0009] Accordingly, one object of the present invention is to provide animproved graft ligament anchor which is relatively simple inconstruction and therefore inexpensive to manufacture, relatively easyto handle and install, and reliable and safe in operation.

[0010] Another object of the present invention is to provide an improvedmethod for attaching a graft ligament to a bone.

SUMMARY OF THE INVENTION

[0011] These and other objects of the present invention are addressed bythe provision and use of a novel graft ligament anchor comprising graftligament engagement means for disposition in an opening in a bone, suchthat a wall of the graft ligament engagement means resides adjacent toat least one graft ligament disposed in the opening, and locking meansfor disposition in the opening in the bone and at least partiallyengageable with the graft ligament engagement means. The elements of thegraft ligament anchor are adapted such that movement of the lockingmeans in the opening in the bone causes at least a part of the lockingmeans to engage the graft ligament engagement means so as to urge thegraft ligament engagement means, and hence the portion of the graftligament disposed adjacent thereto, toward a wall of the opening in thebone, whereby to secure the graft ligament to the wall of the opening.

[0012] In use, an opening is made in the bone, and the graft ligamentand the graft ligament engagement means are inserted into the opening,with a portion of the graft ligament being disposed alongside a wall ofthe graft ligament engagement means. In accordance with the presentinvention, the locking means are also positioned in the opening in thebone, alongside the graft ligament engagement means, with the lockingmeans being separated from the graft ligament by a portion of the graftligament engagement means. The method further includes moving thelocking means in the opening in the bone so as to cause at least aportion thereof to urge the graft ligament engagement means, and hencethe portion of the graft ligament disposed adjacent thereto, toward awall of the opening, whereby to secure the graft ligament to the wall ofthe opening.

[0013] In one aspect of the invention, a graft fixation device forfixing a graft member within a bone tunnel includes a radiallyexpandable sheath having a side wall with at least one structurallyweakened fracture region extending longitudinally along a length of thesheath in the side wall. The radially expandable sheath is sized to fitwithin a bone tunnel so that a graft member may be accommodated betweena wall of a bone tunnel and an outer surface of the radially expandablesheath. A sheath expander is disposable in a central lumen of theradially expandable sheath to radially expand the sheath so as to fixthe graft member within the bone tunnel. The structurally weakenedfracture region is adapted to fracture upon radial expansion of thesheath to allow varying amounts of radial expansion.

[0014] In specific embodiments of this aspect of the invention, a numberof longitudinal side wall segments can be provided, the segments beingconnected by longitudinal fracture regions. The side wall segments canalso have concave outer surfaces so that each segment can capture aportion of graft material between its outer surface and the bone tunnelwall. In a further embodiment, the segments can be longitudinallydivided into subsegments connected by longitudinal flexion regions.

[0015] In another aspect of the invention, a graft fixation device forfixing a graft member within a bone tunnel includes a radiallyexpandable sheath having a side wall comprising a plurality oflongitudinal side wall segments separated by convex longitudinal flexregions having convex outer surfaces, the radially expandable sheathbeing sized to fit within a bone tunnel and defining a central lumen. Inthis aspect, the side wall segments are flexible and have a concaveouter surface adapted to enclose a graft member between the concaveouter surface and a bone tunnel wall. A sheath expander is disposable inthe central lumen of the radially expandable sheath to flex the convexlongitudinal flex regions and the flexible concave wall segments toradially expand the sheath so as to fix a graft member within a bonetunnel.

[0016] In specific embodiments of this aspect, the side wall segmentsmay include rigid longitudinal subsegments connected by longitudinalflex regions to provide flexing within the segments. In addition, convexlongitudinal flex regions may be configured to flex, but then fractureto allow further radial expansion of the sheath.

[0017] Graft fixation devices of the invention allow a wider variety ofmaterials to be used to form the radially expanding sheath and can alsoallow a single sized sheath to be used with a larger variety of bonetunnel and expander sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] These and other objects and features of the present inventionwill be more fully disclosed or rendered obvious by the followingdetailed description of the preferred embodiments of the invention,which are to be considered together with the accompanying drawingswherein like numbers refer to like parts, and further wherein:

[0019]FIG. 1 is a diagrammatic sectional view of one form of graftligament anchor made in accordance with the present invention;

[0020]FIG. 2 is similar to FIG. 1, but shows the graft ligament anchorcomponents in different operating positions;

[0021]FIG. 3 is similar to FIG. 1, but shows an alternative embodimentof the present invention;

[0022]FIG. 4 is a diagrammatic sectional view of another form of graftligament anchor made in accordance with the present invention;

[0023]FIG. 5 is similar to FIG. 4, but shows the graft ligament anchorcomponents in different operating positions;

[0024]FIG. 6 is a diagrammatic sectional view of another form of graftligament anchor made in accordance with the present invention;

[0025]FIG. 7 is a diagrammatic sectional view of still another form ofgraft ligament anchor made in accordance with the present invention;

[0026]FIG. 8 is a diagrammatic sectional view of yet another form ofgraft ligament anchor made in accordance with the present invention;

[0027]FIG. 9 is a perspective view of one of the components of the graftligament anchor shown in FIG. 8;

[0028]FIG. 10 is a diagrammatic sectional view of still another form ofgraft ligament anchor made in accordance with the present invention;

[0029]FIG. 11 is a diagrammatic view of still another form of graftligament anchor made in accordance with the present invention;

[0030]FIG. 12 is a diagrammatic sectional view of yet another form ofgraft ligament anchor made in accordance with the present invention;

[0031]FIG. 13 is similar to FIG. 12, but shows the graft ligament anchorcomponents in different operating conditions;

[0032]FIG. 13A is a diagrammatic sectional view of still another form ofligament anchor made in accordance with the present invention;

[0033]FIG. 14 is a top plan view of still another form of graft ligamentanchor made in accordance with the present invention;

[0034]FIG. 15 is a side view, in section, of the graft ligament anchorshown in FIG. 14;

[0035]FIG. 16 is a side view showing the graft ligament anchor of FIGS.14 and 15 securing a graft ligament to a bone;

[0036]FIG. 17 is similar to a portion of FIG. 16, but showing componentsof the graft ligament anchor and graft ligament of FIG. 16 inalternative positions;

[0037]FIG. 18 is a top plan view of yet another form of graft ligamentanchor made in accordance with the present invention;

[0038]FIG. 19 is a side view, in section, of the graft ligament anchorshown in FIG. 18;

[0039]FIG. 20 is a diagrammatic sectional view of still another form ofgraft ligament anchor made in accordance with the present invention;

[0040]FIG. 21 is a perspective view of a component of the graft ligamentanchor shown in FIG. 20;

[0041]FIG. 22 is a diagrammatic sectional view of still another form ofgraft ligament anchor made in accordance with the present invention;

[0042]FIG. 23 is a perspective view of components of the graft ligamentanchor of FIG. 22;

[0043]FIG. 24 is a perspective view of a radially expandable sheath inaccordance with a further embodiment of the invention;

[0044]FIG. 25A is a side view of the sheath of FIG. 24;

[0045]FIG. 25B is a cross-sectional view of the sheath of FIG. 25A takenalong line A-A′ in an unexpanded state;

[0046]FIG. 26 is an exploded view of the radially expandable sheath ofFIG. 24 and a sheath expander;

[0047]FIG. 27 is a cross-sectional view of the radially expandablesheath of FIG. 24 with graft material placed in a bone tunnel prior tofixation; and

[0048]FIG. 28 is a cross-sectional view of the sheath and graft materialof FIG. 27 in after fixation within the bone tunnel.

DETAILED DESCRIPTION OF THE INVENTION

[0049] Referring first to FIG. 1, it will be seen that one illustrativeembodiment of the present invention includes a graft ligament engagementmeans 20 comprising a deformable sleeve 22, preferably formed out ofmetal or plastic, and adapted to be inserted into an opening 24 formedin a bone B. One or more graft ligaments 28 are disposed alongside aninterior wall 30 of sleeve 22.

[0050] The embodiment illustrated in FIG. 1 further includes lockingmeans 32, which may be a pivotally movable rocker arm 34, which may beprovided with a slot 36 for receiving a key member (not shown) forturning rocker arm 34.

[0051] Referring to FIG. 2, it will be seen that turning rocker arm 34enables a portion of the rocker arm to impinge upon an exterior surface40 of sleeve 22 so as to force sleeve 22, and hence graft ligaments 28contained therein, toward sidewall 38 of opening 24, whereby to securesleeve 22 and graft ligaments 28 between opening sidewall 38 and lockingmeans 32.

[0052] In operation, opening 24 is first made in bone B and then graftligaments 28 and graft ligament engagement means 20 are inserted intoopening 24, with graft ligaments 28 being disposed alongside a firstwall, i.e., the interior wall 30, of sleeve 22. Locking means 32 areinserted into opening 24 alongside the exterior surface 40 of sleeve 22.Locking means 32 are thus separated from graft ligaments 28 by graftligament engagement means 20, i.e., sleeve 22. As noted above, movementof locking means 32 causes at least a portion thereof to engage sleeve22 and to crimp the sleeve inwardly upon graft ligaments 28, and to pushboth sleeve 22 and graft ligaments 28 against sidewall 38 of opening 24.

[0053] If it is desired to thereafter release graft ligaments 28, rockerarm 34 may be moved back to the position shown in FIG. 1. To this end,graft ligament engagement means 20 preferably are formed out of aresilient material, whereby engagement means 20 can return tosubstantially the same position shown in FIG. 1 when locking means 32return to the position shown in FIG. 1.

[0054] If desired, substantially all of sleeve 22 can be formed so as tobe deformable; alternatively, some of sleeve 22 can be formed so as tobe rigid. By way of example, the portion of sleeve 22 contacted bylocking means 32 can be formed so as to be substantially rigid.

[0055] Graft ligaments 28 may comprise natural or synthetic graftligament material, and the anchor can be used to attach natural orsynthetic graft ligaments and/or tendons to bone. Sleeve 22 preferablyis provided with inwardly-extending protrusions 42, such as spikes 44,for securely retaining graft ligaments 28 therein.

[0056] Locking means 32 may be a rocker arm type, such as the rocker armmember 34 shown in FIGS. 1 and 2, or a generally conically-shapedexpansion plug 46, as shown in FIG. 3, with the expansion plugpreferably being threaded such that as the plug is screwed into place,an increasing diameter of the plug engages sleeve 22 in a wedge-likemanner so as to force the sleeve against interior wall 38 of opening 24.

[0057] In FIG. 4, there is shown an alternative embodiment in whichgraft ligaments 28 are disposed alongside exterior wall 40 of sleeve 22,and locking means 32 is disposed within sleeve 22. With this embodiment,locking means 32 operate to engage interior wall 30 of the sleeve (FIG.5), whereby to force graft ligaments 28 against sidewall 38 of opening24. Again, locking means 32 may be a rocker arm type, such as the rockerarm member 34 shown in FIGS. 4 and 5, or may be an expansion plug 46,preferably threaded, of the sort shown in FIG. 3. With the embodimentshown in FIGS. 4 and 5, sleeve 22 may be provided with protrusions 42(in the form of spikes 44, for example) on the exterior wall 40 thereoffor engagement with graft ligaments 28. In many instances, it isbeneficial to provide at least two discrete graft ligaments 28 and, insuch cases, it is preferable that the graft ligaments be disposed onsubstantially opposite diametric sides of the sleeve, as shown in FIGS.4 and 5.

[0058] In FIG. 6, there is shown an embodiment similar to that shown inFIGS. 4 and 5, but provided with an expandable sleeve 22A, rather than adeformable metal or plastic sleeve 22 as shown in FIGS. 1-5. Sleeve 22Amay be formed out of an elastomeric material, and it is expandedradially outwardly by engagement with a centrally disposed locking means32 (preferably in the form of a threaded expansion plug 46) so as toforce graft ligaments 28 outward into a secured position between sleeve22A and opening sidewall 38.

[0059] In operation, the embodiments shown in FIGS. 4-6 functionsimilarly to the embodiments shown in FIGS. 1-3 in attaching graftligaments 28 to bone B. Opening 24 is first made in bone B. Graftligaments 28 and graft ligament engagement means 20 (in the form ofsleeve 22 or sleeve 22A) are inserted into opening 24, with graftligaments 28 disposed alongside exterior wall 40 of the graft ligamentengagement means, i.e., alongside the exterior wall 40 of sleeve 22 orsleeve 22A. Locking means 32 (in the form of a rocker arm member 34 or athreaded expansion plug 46) are inserted axially into the sleeve,alongside interior wall 30 of the sleeve. Locking means 32 are thusseparated from the graft ligaments 28 by the sleeve (22 or 22A). Thenlocking means 32 are manipulated so as to engage the sleeve (22 or 22A)and thereby urge the sleeve, and hence graft ligaments 28, towardopening sidewall 38, whereby to secure the sleeve and graft ligaments tothe wall of the opening.

[0060] If and when it is desired to adjust tension on graft ligaments28, locking means 32 may be backed off, that is, if locking means 32comprise the rocker arm type cam member 34, the arm need only be rotated90° from the positions shown in FIGS. 2 and 5, to return to thepositions shown, respectively, in FIGS. 1 and 4; if, on the other hand,locking means 32 comprise expansion plug 46, the plug need only beunscrewed or otherwise axially withdrawn so as to release the securingof the graft ligaments.

[0061] Referring next to FIG. 7, it will be seen that in an alternativeembodiment, graft ligament engagement means 20 comprises plate means 48which are movable transversely within the bone opening. As in theembodiments previously described, graft ligaments 28 are disposedalongside a wall 50 of graft ligament engagement means 20, which in thisinstance is a first major surface of plate means 48. Graft ligamentengagement means 20 are disposed between graft ligaments 28 and lockingmeans 32. Locking means 32 may be, as in the above-describedembodiments, an expansion plug 46 (as shown in FIG. 7), or locking means32 may be a rocker arm type of cam member 34 (of the sort shown in FIGS.1, 2, 4 and 5). Locking means 32 are adapted to impinge upon a secondmajor surface 52 of plate means 48. Plate means 48, in the embodimentshown in FIG. 7, comprises a single plate 54 having, on first majorsurface 50 thereof, one or more concavities 56 for nesting one or moregraft ligaments 28, respectively.

[0062] In the attachment of one or more graft ligaments 28 to a bone B,using the embodiment of FIG. 7, locking means 32 are manipulated so asto bear against plate 54 so as to move plate 54 into engagement withgraft ligaments 28, and thence to further move plate 54 so as to securethe graft ligaments against sidewall 38 of opening 24.

[0063] Referring next to FIG. 8, it will be seen that locking means 32may comprise the threaded expansion plug 46 deployed partly in opening24 and threaded partly into bone B, thus serving as a so-calledinterference screw. With this arrangement, plug 46 is thereby (i) inpart along its length disposed in opening 24, protruding into theopening from opening wall 38, and (ii) in part along its lengththreadedly engaged with bone B. Screwing in plug 46 causes the plug toengage plate 54 which, in turn, compacts one or more graft ligaments 28against wall 38 of opening 24.

[0064] In lieu of, or in addition to, the aforementioned concavities 56shown in FIG. 7, plate 54 may be provided with gripper ribs 58 forengaging graft ligaments 28, as shown in FIGS. 8 and 9.

[0065] In FIG. 10, it is shown that plate means 48 may include first andsecond plates 60, 62, each having a wall 50 facing one or more graftligaments 28, and a wall 52 facing locking means 32. Plates 60, 62 maybe joined together by a link 64 which may be molded integrally withplates 60, 62 so as to form a so-called “living hinge” link. Lockingmeans 32 are depicted in FIG. 10 as a rocker arm type of cam member 34,but it will be appreciated that an expansion plug type of locking means(e.g., a plug 46 such as that shown in FIGS. 3, 6 and 7) might also beused.

[0066] In operation, rotative movement of rocker arm 34 (or axialmovement of expansion plug 46) causes plates 60, 62 to move outwardlyfrom each other so as to urge graft ligaments 28 against wall 38 ofopening 24. Walls 50 of plates 60, 62 may be provided with concavities56, as shown in FIG. 10, or with ribs 58 of the sort shown in FIG. 9, orboth.

[0067] Referring next to FIG. 11, it will be seen that still anotherembodiment of the present invention includes, as graft ligamentengagement means 20, a V-shaped strip 94, preferably made out of aresilient metal or plastic material. An end portion 96 of a graftligament 28 is disposed between first and second leg portions 98, 100 ofV-shaped strip 94, and graft ligament 28 extends alongside an exteriorsurface 102 of second leg portion 100. Locking means 32 comprise athreaded expansion plug 46 disposed partly in opening 24 and partly inbone B, along sidewall 38 of opening 24, in a manner similar to thedisposition of threaded expansion plug 46 shown in FIG. 8.

[0068] Upon screwing in expansion plug 46, the expansion plug engagesfirst leg 98 of graft ligament engagement means 20 (i.e., the V-shapedstrip 94) to force first leg 98 to close upon second leg 100 with thegraft ligament end portion 96 sandwiched therebetween and, upon furtherscrewing in of threaded expansion plug 46, to force graft ligamentengagement means 20 and graft ligament 28 against wall 38 of opening 24.To release graft ligament 28, an operator need only back out expansionplug 46.

[0069] When attaching a graft ligament to a bone with the graft ligamentanchor shown in FIG. 11, an opening is first drilled, or otherwise made,in the bone. Then the V-shaped strip 94 is inserted into the opening,with a nose portion 104 thereof pointed inwardly of the bone. Next, endportion 96 of graft ligament 28 is inserted between first and second legportions 98, 100 of V-shaped strip 94. Threaded expansion plug 46 isthen inserted into opening wall 38 such that a first portion 106 of thelengthwise extent of plug 46 is disposed in opening 24, and secondportion 108 of the lengthwise extent of plug 46 is threadedly engagedwith bone B. Expansion plug 46 is then screwed further down so as tocause plug 46 to engage first leg 98 of V-shaped strip 94 so as tosecure graft ligament end portion 96 in V-shaped strip 94, and thenscrewed down further to wedge strip 94 and graft ligament 28 againstwall 38 of opening 24.

[0070] Still referring to FIG. 11, it is to be appreciated that boneopening 24 may be formed with a constant diameter throughout its lengthor, if desired, may be formed with two different diameters along itslength, in the manner shown in FIG. 11, so as to form an annularshoulder 110 within the bone opening. The provision of an annularshoulder 110 can be very helpful in ensuring that the graft ligamentanchor is prevented from migrating further into bone B, even if graftligament 28 should thereafter be subjected to substantial retractionforces.

[0071] In a modification (not shown) of the FIG. 11 embodiment, theexpansion plug 46 may be entered alongside graft ligament 28 and secondleg portion 100 of strip 94. In this modified version, the expansionplug 46 operates as described above, except that expansion plug 46engages graft ligament 28 and forces strip first leg 98 against wall 38of opening 24.

[0072] Looking next at FIGS. 12 and 13, yet another form of graftligament anchor is disclosed. This graft ligament anchor is similar tothe embodiment shown in FIG. 6, except that the expandable sleeve 22B isin the form of a cylindrical coil. Sleeve 22B is formed out of anelastomeric material and is expanded radially outwardly by engagementwith a centrally disposed locking means 32 (preferably anaxially-movable threaded expansion plug 46) so as to force graftligament 28 outward into a secured position between sleeve 22B and boneB.

[0073] In FIG. 13A there is shown an embodiment similar to that shown inFIG. 10, but in which the first and second plates 60, 62 are discreteplates and not connected to each other. With this arrangement, lockingmeans 32 is inserted into a central recess 74 defined by plate walls 52,and may comprise either an expansion plug 46 of the type shown in FIGS.6 and 7 or a rocker arm type of cam member 34 of the type shown in FIGS.1 and 2.

[0074] Looking next at FIGS. 14 and 15, another graft ligament anchor200 is shown. Anchor 200 includes graft ligament engagement means 20comprising a flat plate 201, a pair of through-holes 202, 204 and athreaded through-hole 206. In use, and looking now at FIGS. 14, 15 and16, the free end 96 of graft ligament 28 is passed downward through hole202 and then back upward again through hole 204, and then a screw 208 isused to secure anchor 200 to the wall 210 of the bone opening bythreading the shank of screw 208 through hole 206, through graftligament 28, and into bone B. This will cause screw 208 and plate 201 tosecurely attach graft ligament 28 to bone B.

[0075] As shown in FIG. 17, alternatively, graft ligament 28 may bepassed upwardly through hole 202 and downwardly through hole 204. Screw208 is then threaded through hole 206 and graft ligament 28 and intobone B. Thus, as in the embodiment shown in FIG. 16, screw 208 and plate201 secure graft ligament 28 to bone B.

[0076]FIGS. 18 and 19 show another graft ligament anchor 200A. Graftligament anchor 200A is similar to graft ligament anchor 200, exceptthat it includes a plurality of spikes 212 for projecting into wall 210(FIG. 16) of bone B when the graft ligament anchor is deployed againstthe bone. Also, graft ligament anchor 200A has an enlarged configuration214 in the region of through-hole 206A, as shown in FIG. 18.

[0077] Referring next to FIG. 20, there is shown a still furtheralternative embodiment of graft ligament anchor, similar to that shownin FIG. 7, wherein graft ligament engagement means 20 comprises platemeans 48 formed in a U-shaped configuration (FIG. 21) movabletransversely within bone opening 24. At least one graft ligament 28 isdisposed alongside wall 50 of graft ligament engagement means 20, whichin this instance is a first major surface of plate means 48. Graftligament engagement means 20 is disposed between graft ligament 28 andlocking means 32. Locking means 32 may be an expansion plug 46, as shownin FIG. 20 and in FIG. 7, or a rocker arm type cam member 34, as shownin FIG. 1, or an interference screw type expansion plug 46, as shown inFIG. 11, or a transverse screw 208, as shown in FIG. 16.

[0078] In attachment of one or more graft ligaments 28 to a bone B,using the embodiment of FIG. 20, locking means 32 is manipulated so asto bear against a second major surface 52 of plate means 48 and therebymove plate means 48 into engagement with graft ligament 28, and thenceto drive free ends 49 of plate means 48 into sidewall 38 of opening 24so as to fasten graft ligament 28 to sidewall 38 and, thereby, to boneB.

[0079] Referring to FIGS. 22 and 23, there is shown still anotheralternative embodiment of graft ligament anchor including a tubularmember 300, open at first and second ends 302, 304 and having an opening306 in the sidewall thereof. Otherwise, the graft ligament anchor ofFIG. 22 is similar to the graft ligament anchor of FIG. 20, describedhereinabove.

[0080] In attachment of one or more graft ligaments 28 to a bone, usingthe embodiment of FIGS. 22 and 23, locking means 32 are manipulated tobear against second major surface 52 of plate means 48 so as to moveplate means 48 through tubular member opening 306 and into engagementwith graft ligament 28, and thence further to drive free ends 49 ofplate means 48 into sidewall 38 of opening 24, whereby to fasten tubularmember 300 and graft ligament 28 to sidewall 38 and, thereby, to bone B.In this embodiment, and in the embodiments shown in FIGS. 1-3, anoperator may fasten the graft ligament to the bone without the graftligament contacting the bone. The tubular member 300 preferably is of aplastic or metallic material and the plate means 48 is of a plastic ormetallic material. In the embodiments shown in FIGS. 20 and 22, theplate means 48 may be provided with interior teeth 47 for gripping graftligament 28.

[0081] A further embodiment of the present invention is illustrated inFIG. 24-FIG. 28. FIG. 24 shows a perspective view of a selectivelyradially expandable sheath 400 having a side wall 401 and defining acentral lumen 450. As illustrated in FIG. 27, sheath 400 is sized to fitwithin a bone tunnel 600 (FIG. 27) while capturing graft material 28between an outer surface of the sheath and an inner wall of bone tunnel600. Central lumen 450 is sized to accept a sheath expanding element(such as sheath expanding element 700 (FIG. 26) or locking means 32(see, e.g., FIG. 10)) that expands the sheath radially to fix graftmaterial 28 within bone tunnel 600 as illustrated in FIG. 28.

[0082] Referring again to FIG. 24, sheath 400 can include a proximal or“sheath expander lead-in” end region 403 that is tapered to easeinsertion of a sheath expander into central lumen 450. Lead-in region403 may have proximal cut-out areas 406 to facilitate radial expansionin the proximal cross-section of sheath 400. Central lumen 450 may alsoinclude female threads 407 on an inside surface 408 of side wall 401 tofacilitate a threaded engagement with a threaded sheath expander (suchas tapered screw sheath expander 700 (FIG. 26)) in central lumen 450.Lead-in region 403 of sheath 400 can also include a tab 1000 which mayserve as a stop to prevent any overinsertion of sheath 400 into a bonetunnel. The outer diameter of side wall 401 may also taper from a largerdiameter in lead-in region 403 to a smaller diameter at distal tip 409to provide a gradual transition in the amount of ultimate compressiveload being applied to graft members 28 during insertion. As with lead-inregion 403, distal tip 409 may have cut-out areas 452 to facilitateradial expansion in the distal cross-section of sheath 400. A portion ofthe outside surface of side wall 401 may include ribs 402, protrusionsor other similar features which roughen the outside surface and engagewith either or both the wall 600 (FIGS. 27 and 28) of a bone tunnel andgraft material 28 when sheath 400 is expanded.

[0083] As illustrated in the cross-sectional view of FIG. 25B, side wall401 of sheath 400 is divided into four londitudinal side wall segments405, each having concave outer surfaces which provide regions 410, 420,430, and 440 where graft material may be disposed between the side wallsegments and bone tunnel wall 600 (as further illustrated in FIG. 27).In accordance with the principles of the invention, a sheath expander(such as tapered screw sheath expander 700) may be inserted into centrallumen 450 of sheath 400 to deform non-circular side wall 401 toward acircular geometry to conform with an outer diameter of expander 700.Sheath 400 includes a number of features configured to accommodate thisdeformation.

[0084] In particular, sheath 400 can include one or more structurallyweakened fracture regions 490 extending longitudinally along a length ofside wall 401. As used herein, structurally weakened refers to a featurethat can allow flexion and/or fracture side wall 401, in some instancesallowing the wall to flex as if it were hinged (and it is furthercontemplated that a hinge of any type could be a structurally weakenedregion). In a preferred embodiment, fracture regions 490 extendsubstantially along or entirely along the length of side wall 401 andmay incorporate proximal and distal cut outs 406 and 452. Further,fracture regions 490 may be configured to flex to allow some radialexpansion of the sheath before fracturing to allow even further radialexpansion of sheath 400 (post fracture expansion is illustrated in FIG.28). Fracture regions 490 may be formed by thinning the material of sidewall 401 longitudinally in the region of desired fracture, and in oneembodiment, may be a longitudinal groove cut into side wall 401.

[0085] In the illustrative embodiment of FIG. 25B, sheath 400 comprisesfour longitudinal side wall segments 405 that circumscribe central lumen450, each of the longitudinal side wall segments being connected to itsneighbors by the four structurally weakened longitudinal fractureregions 490. While this configuration may be preferred in the situationthat the graft material being fixed to a bone tunnel can easily beseparated into four components, a person of ordinary skill in the artwill recognize that more or fewer side wall segments and structurallyweakened regions can be provided to adapt sheath 400 to differentfixation requirements. In addition, central lumen need not be fullycircumscribed by side wall segments having concave outer surfaces. Forexample, half of side wall 401 could take the form of one half of acylinder generally conforming to the shape of the bone tunnel, while theother half of side wall 401 could comprise two or more side wallsegments 405 having concave outer surfaces, the side wall segments 405being connected to each other and to the half cylinder portion bylongitudinal fracture regions. Such a configuration may be preferablewhere a surgeon wishes to fix the graft material to one side of a bonetunnel (such as an anterior or posterior side) at the expense offixation to the opposed side.

[0086] Concave side wall segments 405 may also include longitudinalflexion regions 480 to aid in allowing the wall segments to expandradially outward to fix graft material to a bone tunnel wall. As withfracture regions 490, flexion regions can extend substantially along orentirely along the length of side wall 401. Flexion regions 480 may alsobe formed by thinning the material of side wall 401 longitudinally inthe region of desired flexion, and in one embodiment, may be alongitudinal groove cut into side wall 401.

[0087] In the illustrated embodiment, each concave side wall segment 405includes two longitudinal flexion regions 480 which divide the wallsegments into three relatively rigid longitudinal subsegments connectedby the two longitudinal flexion regions. A person of ordinary skill inthe art will recognize that a sheath of the invention could be formedusing only one flexion region within a wall segment or by using morethan two such flexion regions within the spirit of the invention.

[0088] In one embodiment of the invention, longitudinal fracture regions490 (which preferably flex before fracturing) have a convex outersurface and act as “outer hinges,” while longitudinal flexion regions480 act as “inner hinges” to allow a first measure of radial expansiontoward a circular geometry by flexing of these inner and outer hinges.This first measure of radial expansion can be followed by fracture ofone or more of the longitudinal fracture regions 490 to provide a secondmeasure of radial expansion beyond the first measure.

[0089] The provision of inner 480 and outer 490 hinges in sheath 400provides resiliency and malleability to side wall 401 and allows for theoption of using stiffer, stronger starting stock for sheath 400 thanwould otherwise be possible. Both inner hinge flexion regions 480 andouter hinge fracture regions 490 serve as concentrated bending areas.However, fracture regions 490 are preferably configured to act asregions of maximum stress as there is less or no graft material 28 tocounterbalance radial stresses. If side wall 401 is to fail at anylocation for lack of ductility or strength, this embodiment allows forbreakage to occur at fracture regions 490, further illustrated in FIG.28 after fracture as edges 500. Flexion regions 480, as thinned regions,are preferably configured to add flexibility to side wall segments 405and to facilitate increase of the radius of curvature of the concaveouter surface of segments 405 without undue risk of breakage on segments405 which must carry a compressive load to graft material 28.Accordingly, fracture regions 490 would preferably have a geometry suchthat the local material stresses during expansion of sheath 400 arealways greater than the local stresses at flexion regions 480 so thatmaterial rupture will always be directed along the path of fractureregions 490. This means of controlled rupture ensures that sheath 400will remain biomechanically functional since the rupture will then occuraway from ligament accommodating regions 410, 420, 430, 440.

[0090] Further, such controlled rupture along fracture regions 490facilitates use of a wider variety of expander sizes, including the useof expanders having an outer diameter or circumference at least as largeas the diameter or circumference of sheath 400. In this way, a singlesheath size may be stocked for a wide variety of procedures and intendedbone tunnel sizes. In one embodiment, sheath 400 may be provided in akit to surgeons in which a plurality of expanders having different sizesare provided for use with a single size sheath.

[0091] The inclusion of fracture regions 490 and/or flexion regions 480widen the choice of available sheath materials to include, for example,biocompatible bioabsorbable polymers selected from the group consistingof aliphatic polyesters, polyorthoesters, polyanhydrides,polycarbonates, polyurethanes, polyamides and polyalkylene oxides.Sheath 400 may also be formed from absorbable glasses and ceramics(possibly comprising calcium phosphates and other biocompatible metaloxides (i.e., CaO)). Sheath 400 may also be formed from metals; it cancomprise combinations of metals, absorbable ceramics, glasses orpolymers.

[0092] In further embodiments, the expandable sheath may be fabricatedfrom aliphatic polymer and copolymer polyesters and blends thereof.Suitable monomers include but are not limited to lactic acid, lactide(including L-, D-, meso and D,L mixtures), glycolic acid, glycolide,E-caprolactone, p-dioxanone (1,4-dioxan-2-one), trimethylene carbonate(1,3-dioxan-2-one), delta-valerolactone, beta-butyrolactone,epsilon-decalactone, 2,5-diketomorpholine, pivalolactone, alpha,alpha-diethylpropiolactone, ethylene carbonate, ethylene oxalate,3-methyl-1,4-dioxane-2,5-dione, 3,3-diethyl-1,4-dioxan-2,5-dione,gamma-but yrol act one, 1,4-dioxepan-2-one, 1,5-dioxepan-2-one,6,6-dimethyl-dioxepan-2-one, 6,8-dioxabicycloctane-7-one andcombinations thereof. These monomers generally are polymerized in thepresence of an organometallic catalyst and an initiator at elevatedtemperatures. The organometallic catalyst may be tin based, (e.g.,stannous octoate), and may be present in the monomer mixture at a molarratio of monomer to catalyst ranging from about 10,000/1 to about100,000/1. The aliphatic polyesters are typically synthesized in aring-opening polymerization process. The initiator is typically analkanol (including diols and polyols), a glycol, a hydroxyacid, or anamine, and is present in the monomer mixture at a molar ratio of monomerto initiator ranging from about 100/1 to about 5000/1. Thepolymerization typically is carried out at a temperature range fromabout 80° C. to about 240° C., preferably from about 100° C. to about220° C., until the desired molecular weight and viscosity are achieved.

[0093] It is to be understood that the present invention is by no meanslimited to the particular constructions and methods herein disclosedand/or shown in the drawings, but also comprises any modifications orequivalents within the scope of the claims

What is claimed is:
 1. A graft fixation device for fixing a graft memberwithin a bone tunnel, the device comprising: a radially expandablesheath having a side wall, at least one structurally weakened fractureregion extending longitudinally along a length of the sheath in the sidewall, and a central lumen, the radially expandable sheath sized to fitwithin a bone tunnel so that a graft member may be accommodated betweena wall of a bone tunnel and an outer surface of the radially expandablesheath; and a sheath expander disposable in the central lumen of theradially expandable sheath to radially expand the sheath so as to fix agraft member within a bone tunnel; wherein the structurally weakenedfracture region is adapted to fracture upon radial expansion of thesheath to allow varying amounts of radial expansion.
 2. The graftfixation device of claim 1, wherein the sheath side wall comprises aplurality of longitudinal wall segments separated by structurallyweakened fracture regions extending longitudinally along a length of thesheath, each structurally weakened fracture region being adapted tofracture upon radial expansion of the sheath to allow varying amounts ofradial expansion.
 3. The graft fixation device of claim 2, wherein thelongitudinal wall segments have concave outer surfaces.
 4. The graftfixation device of claim 3, wherein the longitudinal wall segmentsinclude at least one structurally weakened flexion region extendinglongitudinally along a length of the wall segments, the structurallyweakened flexion regions adapted to flex so as to permit the concaveouter surfaces of the wall segments to expand outwardly.
 5. The graftfixation device of claim 4, wherein the structurally weakened flexionregions are adapted not to fracture upon flexing.
 6. The graft fixationdevice of claim 4, wherein the structurally weakened fracture regionsare adapted to flex prior to fracturing upon radial expansion.
 7. Thegraft fixation device of claim 4, wherein each longitudinal wall segmentincludes two structurally weakened flexion region extendinglongitudinally along a length of the wall segment, thereby dividing thewall segment into three rigid, longitudinal wall subsegments connectedto each other by structurally weakened flexion regions.
 8. The graftfixation device of claim 2, wherein the wall segments circumscribe thecentral lumen.
 9. The graft fixation device of claim 8, wherein fourwall segments circumscribe the central lumen.
 10. The graft fixationdevice of claim 1, wherein the structurally weakened fracture regionsare regions that are more thin than other side wall regions.
 11. Thegraft fixation device of claim 1, wherein the structurally weakenedfracture regions comprise grooves formed in the side wall.
 12. The graftfixation device of claim 1, wherein the sheath expander is a taperedscrew.
 13. The graft fixation device of claim 12, wherein the sheathexpander has a largest circumference that is at least as large as alarges outer circumference of the radially expandable sheath in anunexpanded state.
 14. A graft fixation device for fixing a graft memberwithin a bone tunnel, the device comprising: a radially expandablesheath having a side wall comprising a plurality of longitudinal sidewall segments separated by convex longitudinal flex regions havingconvex outer surfaces, the radially expandable sheath being sized to fitwithin a bone tunnel and defining a central lumen; each side wallsegment being flexible and having a concave outer surface adapted toenclose a graft member between the concave outer surface and a bonetunnel wall; and a sheath expander disposable in the central lumen ofthe radially expandable sheath to flex the convex longitudinal flexregions and the flexible concave wall segments to radially expand thesheath so as to fix a graft member within a bone tunnel.
 15. The graftfixation device of claim 14, wherein the flexible side wall segmentsinclude at least one longitudinal flexion region extendinglongitudinally along a length of the wall segments, the longitudinalflexion regions adapted to flex so as to permit the concave outersurfaces of the wall segments to expand outwardly.
 16. The graftfixation device of claim 15, wherein the flexible side wall segmentsinclude two longitudinal flexion regions that divide the wall segmentsinto three rigid longitudinal side wall subsegments connected by the twolongitudinal flexion regions.
 17. The graft fixation device of claim 14,wherein the convex longitudinal flex regions are adapted to fractureupon radial expansion of the sheath to allow varying degrees of radialexpansion.
 18. The graft fixation device of claim 14, wherein theradially expanding sheath includes four longitudinal side wall segments.19. The graft fixation device of claim 14, wherein the longitudinal sidewall segments circumscribe the central lumen.
 20. The graft fixationdevice of claim 14, wherein the sheath expander is a tapered screw. 21.The graft fixation device of claim 20, wherein the sheath expander has alargest circumference that is at least as large as a larges outercircumference of the radially expandable sheath in an unexpanded state.